Multi-cell inductive wireless power transfer system

ABSTRACT

A multi-cell inductive wireless power transfer system includes multiple transmitting elements. Each transmitting element includes one or more transmitting windings and one or more transmitting magnetic cores. The multi-cell inductive wireless power transfer system also includes multiple receiving elements. The transmitting elements are separated from the receiving elements by an air gap. Each receiving element includes one or more receiving windings and one or more receiving magnetic cores.

BACKGROUND

The present disclosure relates to power transfer systems, and moreparticularly, to wireless power transfer systems.

Inductively-coupled power transfer is gaining acceptance in military andcommercial applications. Evolving undersea systems, for example, serve avariety of military and commercial applications including datacommunication networks, object sensing and detection systems, andvehicle hub systems. To achieve these wide-ranges of applications,conventional inductively-coupled power transfer devices aim to employ anuncomplicated and robust power interface to facilitate practical energytransfer.

SUMMARY

According to a non-limiting embodiment, a multi-cell inductive wirelesspower transfer system includes multiple transmitting elements. Eachtransmitting element includes one or more transmitting windings and oneor more transmitting magnetic cores. The multi-cell inductive wirelesspower transfer system also includes multiple receiving elements. Thetransmitting elements are separated from the receiving elements by anair gap. Each receiving element includes one or more receiving windingsand one or more receiving magnetic cores.

According to another non-limiting embodiment, a power converter systemcomprises a multi-cell inductive wireless power transfer systemincluding a plurality of transmitting elements, a plurality of receivingelements, a transmitting power converting circuit, and a receiving powerconverting circuit. Each transmitting element includes at least onetransmitting winding and at least one transmitting magnetic core. Eachreceiving element includes at least one receiving winding and at leastone receiving magnetic core. The transmitting power converting circuitis configured to convert an input power signal into a transmitting powersignal to drive the plurality of transmitting elements. The receivingpower converting circuit is configured to convert a transferred powersignal received at the plurality of receiving elements into an outputpower signal to drive an electrical load.

According to yet another non-limiting embodiment, a power chargingsystem comprises a charging station capable of recharging a vehicle thatmoves independent of the charging station. The charging station includesa plurality of transmitting elements. Each transmitting element includesat least one transmitting winding and at least one transmitting magneticcore. The vehicle includes a plurality of receiving elements. Eachreceiving element includes at least one receiving winding and at leastone receiving magnetic core.

According to still another non-limiting embodiment, a method is providedto control a power charging system. The method comprises generating amagnetic field via at least one transmitting element among a pluralityof transmitting elements installed in a charging station. The magneticfield is generated in response to energizing at least one transmittingwinding arranged adjacent to at least one transmitting magnetic coreincluded in the at least one transmitting element. The method furthercomprises positioning a vehicle including at least one receiving elementamong a plurality of receiving elements in proximity of the magneticfield. The magnetic field energizes at least one receiving windingarranged adjacent to at least one receiving magnetic core included inthe at least one receiving element. The method further comprisesgenerating an output power in response to energizing the least onereceiving element, and charging a battery of the vehicle based on theoutput power.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts:

FIGS. 1A and 1B illustrate a single-cell, single-coil inductive wirelesspower transfer system;

FIG. 2 illustrates the magnetic coupling and stray magnetic fieldsoccurring in a single-cell, single-coil inductive wireless powertransfer system;

FIGS. 3A and 3B illustrate a multi-cell, single-coil inductive wirelesspower transfer system according to a non-limiting embodiment;

FIG. 4 illustrates the increased magnetic coupling and reduced straymagnetic fields resulting from a multi-cell, single-coil inductivewireless power transfer system according to a non-limiting embodiment;

FIGS. 5A and 5B illustrate a multi-cell, dual-coil inductive wirelesspower transfer system according to a non-limiting embodiment;

FIG. 6 illustrates a power converter configured to drive a multi-cellinductive wireless power transfer system according to a non-limitingembodiment;

FIG. 7A illustrates an autonomous unmanned vehicle (UV) including amulti-cell dual-coil inductive wireless receiving system and a UVcharging system including a multi-cell dual-coil inductive wirelesstransmitting system according to a non-limiting embodiment;

FIG. 7B illustrates the autonomous unmanned vehicle (UV) of FIG. 7Abeing docked with the UV charging system according to a non-limitingembodiment;

FIG. 8 illustrates an autonomous unmanned vehicle (UV) including amulti-cell triple-coil inductive wireless receiving system and a UVcharging system including a multi-cell triple-coil inductive wirelesstransmitting system according to a non-limiting embodiment;

FIG. 9A illustrates an autonomous unmanned vehicle (UV) includingmultiple cells having receiving coils with phases that are misalignedwith respect to transmitting coils of a UV charging system;

FIG. 9B illustrates the autonomous unmanned vehicle (UV) includingmultiple cells having receiving coils with phases that are activelyreconfigured to be synchronized with respect to the transmitting coilsof the UV charging system;

FIG. 10A is a signal diagram illustrating the output power followingloss of a phase signal included in a multi-cell inductive wireless powertransfer system; and

FIG. 10B is a signal diagram illustrating the output power afterrestoring balance of the phase signal in the multi-cell inductivewireless power transfer system.

DETAILED DESCRIPTION

Single-cell power transfer systems 100 (see FIGS. 1A-1B) have beendeveloped to facilitate inductively-coupled energy transfer between asingle transmitting coil and a single receiving coil. These single-cellpower transfer systems 100 include a single transmitting (XMT) element102 and a single receiving (RCV) element 104, which together output asingle-phase power signal 10. The transmitting element 102 contains atransmitting coil 106 and a transmitting magnetic core 108. Thereceiving element 104 contains a receiving coil 110 and a receivingmagnetic core 112. The transmitting element 102 and the receivingelement 104 are separated from each other by a distance (d), but caninductively transfer energy between one another. The use of single-cellsdriven by a single-phase signal, produces a strongly fluctuating inputand output power along with excessive stray magnetic fields 116contributing to inefficient energy transfer (see FIG. 2).

Various non-limiting embodiments described herein provide a multi-cellinductive wireless power transfer system capable of improving theefficiency of power transfer between the transmitting elements and thereceiving elements, while reducing the amount of stray magnetic fields.In this manner, an inductive wireless power transfer system havingreduced volume of energy transfer components is provided compared tosingle-cell power transfer systems.

Turning now to FIGS. 3A and 3B, a multi-cell, single-coil inductivewireless power transfer system 300 is illustrated according to anon-limiting embodiment. The multi-cell, single-coil inductive wirelesspower transfer system 300 includes a first transmitting element 302 a, asecond transmitting element 302 b, a first receiving element 304 a and asecond receiving element 304 b. The first and second transmittingelements 302 a and 302 b are separated from the first and secondreceiving elements 304 a and 304 b by an air gap, which defines aseparation distance (d). For example, the distance (d) between thetransmitting elements 302 a and 302 b with diameter of about 60 to 80 mmand the receiving elements 304 a and 304 b with diameter of about 40 to60 mm, respectively can range, for example, from about 10 millimeters(mm) to about 20 mm. By providing multiple transmission elements 302 aand 302 b and multiple receiving elements 304 a and 304 b, themulti-cell inductive wireless power transfer system 300 can output amulti-phase (e.g., two-phase) power signal 305, as opposed to asingle-phase output power signal (see FIG. 2).

The first transmitting element 302 a includes a first transmittingwinding 306 a and a first transmitting magnetic core 308 a. The secondtransmitting element 302 b includes a second transmitting winding 306 band a second transmitting magnetic core 308 b. In at least oneembodiment, the first transmitting winding 306 a is vertically arranged(e.g., stacked) with respect to the first transmitting magnetic core 308a, and the first transmitting winding 306 a is formed on a firstinsulating layer 320 a (see FIG. 3B). An air gap can separate the firsttransmitting winding 306 a from the first transmitting magnetic core 308a by a distance (d). Similarly, the second transmitting winding 306 b isvertically arranged (e.g., stacked) with respect to the second magnetictransmitting core 308 b. The second transmitting winding 306 b is formedon a second insulating layer 320 b (see FIG. 3B), and an air gap canseparate the second transmitting winding 306 b from the secondtransmitting magnetic core 308 b by a distance (d).

The first receiving element 304 a includes a first receiving winding 310a and a first receiving magnetic core 312 a. The second receivingelement 304 b includes a second receiving winding 310 b and a secondreceiving magnetic core 312 b. In at least one embodiment, the firstreceiving winding 310 a is vertically arranged (e.g., stacked) withrespect to the first receiving magnetic core 312 a. The first receivingwinding 310 a is formed on an insulating layer 322 a (see FIG. 3B), andan air gap can separate the first receiving winding 310 a from the firstreceiving magnetic core 312 a. Similarly, the second receiving winding310 b is vertically arranged (e.g., stacked) with respect to the secondmagnetic receiving core 312 b. The second receiving winding 310 b isformed on a second insulating layer 322 b (see FIG. 3B), and an air gapcan separate the second receiving winding 310 b from the secondreceiving magnetic core 312 b.

The transmitting magnetic cores 308 a and 308 b, and the receivingmagnetic cores 312 a and 312 b can be formed from various magneticmaterials such as, for example, a nickel-zinc ferrite material, amanganese-zinc ferrite material, or an alternate material appropriatefor a given application. The windings 306 a and 306 b and 310 a and 310b can each be composed of an electrically conductive material. In atleast one embodiment, the transmitting windings 306 a and 306 b and thereceiving windings 310 a and 310 b have a spiral shape, and are formedas an electrically conductive trace directly on a respective insulatinglayer 320 a, 320 b, 322 a, and 322 b, respectively.

The implementation of multiple cells (N), i.e., multiple transmittingelements 302 a and 302 b and multiple receiving elements 304 a and 304b, allows for overlapping of magnetic field 400, thereby reducing thepower fluctuation between the transmitting elements 302 a and 302 b andthe receiving elements 304 a and 304 b (see FIG. 4). In addition, theamount of stray magnetic fields 402 is reduced, thereby improving theenergy transmission efficiency of the multi-cell inductive wirelesspower transfer system 300.

Although the multi-cell inductive wireless power transfer system 300described above is illustrated having a single winding 306 a, 306 b, 310a, 310 b in each individual element 302 a, 302 b, 304 a, 304 b,respectively, the invention is not limited thereto. Turning to FIGS. 5Aand 5B, for example, a multi-cell, dual-coil inductive wireless powertransfer system 500 according to a non-limiting embodiment. A firsttransmitting element 302 a includes a plurality of transmitting windings306 a and 307 a, and one or more transmitting magnetic cores 308 a. Asecond transmitting element 302 b also includes a plurality oftransmitting windings 306 b and 307 b, and one or more transmittingmagnetic cores 308 b. The secondary elements 304 a and 304 b arestructured in a similar manner. For instance, a first receiving element304 a includes a plurality of receiving windings 310 a and 311 a, andone or more transmitting magnetic cores 312 a. A second receivingelement 304 b also includes a plurality of receiving windings 310 b and311 b, and one or more transmitting magnetic cores 312 b. Although thetransmitting elements 302 a and 302 b, and the receiving elements 304 aand 304 b are illustrated as including two windings, the elements 302 a,302 b, 304 a and 304 b can contain additional windings (3, 5, 7, etc.).Each of the transmitting elements 302 a and 302 b, and the receivingelements 304 a and 304 b can also include multiple magnetic cores 308 a,308 b, 312 a and 312 b.

Although not illustrated, a given transmitting winding 306 a-306 b and307 a-307 b can be vertically arranged with respect to an individualtransmitting magnetic core. Accordingly, the number of transmittingmagnetic cores included in a given transmitting element 302 a and 302 bmatches the number of transmitting windings included in the giventransmitting element 302 a and 302 b. Similarly, a given receivingwinding 310 a-310 b and 311 a-311 b can be vertically arranged withrespect to an individual receiving magnetic core. Accordingly, thenumber of receiving magnetic cores included in a given receiving element304 a and 304 b matches the number of receiving windings included in thegiven receiving element 304 a and 304 b.

Turning now to FIG. 6, a power converter system 600 configured tooperate with a multi-cell inductive wireless power transfer system 300is illustrated according to a non-limiting embodiment. The multi-cellinductive wireless power transfer system 300 includes a plurality oftransmitting elements 302 a and 302 b, and a plurality of receivingelements 304 a and 304 b. Each transmitting element 302 a and 302 bincludes at least one transmitting winding 306 a and 306 b, and at leastone transmitting magnetic core 308 a and 308 b. Similarly, eachreceiving element 304 a and 304 b includes at least one receivingwinding 310 a and 310 b, and at least one receiving magnetic core 312 aand 312 b. In one or more embodiments, the transmitting elements 302 aand 302 b are connected in series with one another, while the receivingelements 304 a and 304 b are connected in a parallel with one another.It should be appreciated, however, that the transmitting elements 302 aand 302 b and the receiving elements 304 a and 304 b can be connected inother configurations without departing from the scope of the invention.

The power converter system 600 further includes a transmitting powerconverting circuit 602 and a receiving power converter circuit 604. Thetransmitting power converting circuit 602 is configured to convert aninput DC power signal (VIN) into a transmitting AC power signal thatdrives the plurality of transmitting elements 302 a and 302 b togenerate a magnetic field 400. The energy of the magnetic field 400 istransferred across an air gap to the receiving elements 304 a and 304 b,where it is utilized to generate a power signal.

Still referring to FIG. 6, the transmitting power converting circuit 602is constructed as a direct current-to-alternating current (DC-AC)converter having an input connected to a DC prime power source toreceive the input power signal (VIN), and an output connected to thetransmitting elements 302 a and 302 b. In at least one embodiment, thetransmitting power converting circuit 602 includes a plurality ofswitches Q1, Q2, Q3 and Q4 connected in a bridge configuration to form afirst bridge 606 of a bi-directional dual active bridge (DAB) circuit.The switches Q1, Q2, Q3 and Q4 can be implemented using a varietyswitching devices including, but not limited to, bipolar transistors,Insulated Gate Bipolar transistors (IGBTs), diodes, relays, and P-typeor N-type Metal Oxide Semiconductor Field Effect Transistors (MOSFETs).In one or more embodiments, the bi-directional DAB circuit 606 alsoincludes a resonant circuit 608 including a capacitor (C_(R1)) connectedin series with an inductor (L_(R)). The resonant circuit 608 can beconnected between a pair of switches (e.g., Q1 and Q2) among theplurality of switches (Q1-Q4) and a transmitting element (e.g., 306 a)among the plurality of transmitting elements (e.g., 306 a and 306 b).

The receiving power converting circuit 604 is configured to convert thetransferred power signal generated by the plurality of receivingelements 304 a and 304 b into an output DC power signal (V_(OUT)) todrive an electrical load. The receiving power converting circuit 604 isconstructed as an AC-DC converter having an input connected to thereceiving elements 304 a and 304 b to receive the transferred powersignal, and an output configured to deliver the DC output power signal(V_(OUT)) to the load. In at least one embodiment, the receiving powerconverting circuit 604 includes a second plurality of switches Q5, Q6,Q7 and Q8 connected in a bridge configuration to form a second bridge610 of the bi-directional DAB circuit. The second plurality of switchesQ5, Q6, Q7 and Q8 can be implemented using a variety switching devicesincluding, but not limited to, bipolar transistors, Insulated GateBipolar transistors (IGBTs), diodes, relays, and P-type or N-type MetalOxide Semiconductor Field Effect Transistors (MOSFETs). In at least oneembodiment, the second DAB circuit 610 includes a capacitor (C_(R2))connected between the receiving elements 304 a and 304 b, and a pair ofswitches (e.g. Q5 and Q6) among the second plurality of switches(Q5-Q8).

In one or more embodiments, the power converter system 600 furtherincludes one or more electronic hardware controllers 612 configured tocontrol the transmitting power converting circuit 602 and the receivingpower converter circuit 604. In at least one embodiment, the controller612 can drive individual elements 302 a-302 b and 304 a-304 b by aphase-shifted signals. The phase shift angle of the signals can bedefined as φ=2πN, where “N” is the number of transmitting elements 302 nand/or receiving elements 304 n controlled by the controller 612. Thecontroller 612 can also actively adjust the phases for the transmittingelements 302 a and 302 b and/or the receiving elements 304 a and 304 bso that so that the transmitting power converting circuit 602 and thereceiving power converter circuit 604 each operate with the same phasefor the clock switching frequency used to drive the switches Q1-Q4 andQ5-Q8.

The controller 612 can also obtain feedback information regarding thetransmitting power converting circuit 602 via a feedback transmittingdata link 614. The feedback information can include, but is not limitedto, the switching frequency of the switches Q1-Q4, the input power(VIN), the output current generated by the transmitting power convertingcircuit 602, and the converted power signal delivered to thetransmitting elements 302 a and 302 b. Based on the feedback data 614,the controller 612 can generate one or more control signals 616 fordriving one or more of the switches Q1-Q4. In at least one embodiment,the control signals 616 can be a phase-shift modulation signal thatactively adjusts the switching time of the switches Q1-Q4.

Similarly, the controller 612 can obtain feedback information regardingthe receiving power converting circuit 604 via a feedback receiving datalink 618. The feedback information can include, but is not limited to,the switching frequency of the switches Q5-Q8, the output power(V_(OUT)), the output current generated by the receiving powerconverting circuit 604, and the transferred power signal generated bythe receiving elements 304 a and 304 b. Based on the feedback data 618,the controller 612 can generate one or more control signals 620 fordriving one or more of the switches Q5-Q8. In at least one embodiment,the control signals 620 can be a phase-shift modulation signal thatactively adjusts the switching time of the switches Q5-Q8.

Turning now to FIGS. 7A and 7B, a power charging system 700 implementinga multi-cell inductive wireless power transfer system is illustratedaccording to a non-limiting embodiment. The power charging system 700includes a charging station 702 configured to transfer energy to avehicle 704. In this manner, a vehicle 704, which moves independentlyand separately from the charging station 702, can be charged to maintainoperational power. The vehicle 704 can include a manned vehicle, orunmanned vehicle (UV). The UV can include, but is not limited to,unmanned aerial vehicles (UAVs), unmanned underwater vehicles (UUVs), orother types of UVs or drones. In any configuration, the vehicle includesa rechargeable battery (e.g., an electrical load) that is charged (i.e.,energized) in response to receiving an output power generated by thepower charging system 700.

The charging station 702 includes a plurality of transmitting elements302 and an electronic hardware transmitting controller 706. Eachtransmitting element 302 includes one or more transmitting windings 306a and 306 b, and one or more transmitting magnetic cores 308. Althoughnot illustrated, the charging station 702 can include a power convertersystem or a portion of the power converter system, e.g., thetransmitting power converting circuit, as described herein (see FIG. 6).Accordingly, the transmitting controller 706 can set the phase of theclock switching frequency used to drive the switches Q1-Q4 of thetransmitting power converting circuit installed in the charging station702. Accordingly, the charging station 702 can generate a magnetic fieldin response to energizing one or more transmitting windings arrangedadjacent to at least one transmitting magnetic core included in atransmitting element (e.g., included in the transmitting powerconverting circuit.

The charging station 702 further includes a dock 708 configured toreceive the vehicle 704. In at least one embodiment, the dock 708 isconstructed as a cavity 708 sized to receive the vehicle 704 therein. Inthis manner, the vehicle 708 can be maneuvered to move into the cavity,thereby being docked (e.g., mechanically coupled) to the chargingstation 702 (see FIG. 7B). Once docked, the vehicle 704 can be rechargedin response to receiving power that is wirelessly transferred from thecharging station 702. Although the dock 708 is described as a cavityformed in the charging station 702, it should be appreciated that otherdesigns capable of mechanically coupling the vehicle 704 in closeproximity to the charging station 702 so as to facilitate wireless powertransfer without departing from the scope of the invention.

The vehicle 704 includes a plurality of receiving elements 304 and areceiving controller 710. Each receiving element 304 includes one ormore receiving windings 310 a and 310 b, and one or more magnetic cores312. Although not illustrated, the vehicle 704 can include a powerconverter system or a portion thereof, e.g., the receiving powerconverter circuit, as described herein (see FIG. 6). The receiving powerconverter circuit can be electrically connected to the rechargeablebattery installed on the vehicle 704. Accordingly, the receivingcontroller 710 can set the phase of the clock switching frequency usedto drive the switches Q5-Q8 of the receiving power converter circuitinstalled in the vehicle 704. The output power generated by thereceiving power converter circuit is then delivered to battery such thatthe battery is recharged.

Although the transmitting elements 302 and receiving elements 304 areillustrated as including two windings 306 a-306 b and 310 a-310 b,respectively, it should be appreciated the more windings can be includedin each element 302 and 304. Turning to FIG. 8, for example, thetransmitting elements 302 and receiving elements 304 can each includethree windings 306 a-306 c and 310 a-310 c, respectively. The additionalwindings can provide redundancy and improve fault-tolerance of theoverall system 700.

In a preferable scenario, the vehicle 704 will dock with the chargingstation 702 such that the receiving elements 304 are aligned with thetransmitting elements 302, and the phase of the receiving elements 304(i.e., the receiving coils 310) match the phase of the transmittingelements 302 (i.e. transmitting coils 306). In some scenarios whenmechanical alignment doesn't match electrical signals, however, one ormore receiving elements 304 assigned a given receiving phase (RCV_(N))may be aligned with a respective transmitting element 302 assigned agiven transmitting phase (XMT_(N-L)). As shown in FIG. 9A, a firsttransmitting element 302 a is set to a first phase (e.g., phase 1),while a close-proximity first receiving element 304 a is initially setto a different phase (e.g., phase 5). Similarly, a second transmittingelement 302 b is set to a second phase (e.g., phase 5), while aclose-proximity second receiving element 304 b is initially set to adifferent phase (e.g., phase 1).

Turning to FIG. 9B, the transmitting controller 706 and the receivingcontroller 710 can communicate with each other to determine the phasesof each receiving element 304, and determine whether the phase (RCV_(N))of a given receiving element 304 n matches the phase (XMT_(N)) of agiven transmitting element 302 n. When the phase of one or morereceiving elements (e.g., 304 a and 304 b) does not match the phase ofits respective transmitting element (e.g., 302 a and 302 b), thetransmitting controller 706 and/or the receiving controller 710 canadjust the phase of the cells. In this manner, the phase of the elements302 and/or 304 can be actively adjusted so that they are brought intophase (i.e., matching phase) with one another as shown in FIG. 9B. Forexample, receiving element 304 a can be reconfigured from phase 5 tophase 1, which matches the phase of transmitting element 302 a.Similarly, receiving element 304 b can be reconfigured from phase 1 tophase 5, which matches the phase of transmitting element 302 b.Accordingly, the output power quality and charging efficiency can beoptimized or improved compared to a system where the phases of thetransmitting elements and receiving elements are mismatched.

The transmitting controller 706 and the receiving controller 710 canalso communicate with each other to determine whether the chargingsystem 700 loses a phase (e.g., a coil fails). FIG. 10A, for example,illustrates the output power generated by a multi-cell inductivewireless power transfer system following loss of one phase (e.g., afailed coil) included in a five-phase system. The loss of a phaseresults creates an unbalanced phase of the total output power signal,which causes in an increased lower frequency ripple, increases stress inthe components, and reduces power transfer efficiency. The increasesripple may also prevent the system from meeting power qualityrequirements and ratings.

When a phase is determined to be lost (e.g., a coil fails), thetransmitting controller 706 and the receiving controller 710 canidentify the lost phase (i.e., failed coil), and reassign remainingphases to a new synchronization frequency to restore the phase balanceof the total output power signal. In this manner, phase balance isrestored with a lower phase, which reduces the previous ripple as shownin FIG. 10B. The transmitting controller 706 and the receivingcontroller 710 can also activate redundant cell or coil, which replacesthe identified failed cell or coil.

As described herein, various non-limiting embodiments provides amulti-cell inductive wireless power transfer system capable of reducingpower fluctuation between the transmitting elements and the receivingelements, while reducing the amount of stray magnetic fields. Themulti-cell inductive wireless power transfer system can be implementedwith a power converter system, capable of actively adjusting the phaseand switching frequency of the switches used to drive the transmittingand/or receiving elements. In this manner, an inductive wireless powertransfer system having improved energy transfer efficiency is providedcompared to single-cell power transfer systems.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiments were chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

While the preferred embodiments to the invention have been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A power converter system comprising: a multi-cellinductive wireless power transfer system, wherein each cell included inthe multi-cell inductive wireless power transfer system comprises aplurality of transmitting elements and a plurality of receivingelements, wherein each transmitting element includes at least onetransmitting winding and at least one transmitting magnetic core, andeach receiving element includes at least one receiving winding and atleast one receiving magnetic core; a transmitting power convertingcircuit configured to convert an input power signal into a transmittingpower signal to drive the plurality of transmitting elements; areceiving power converting circuit configured to convert a transferredpower signal received at the plurality of receiving elements into anoutput power signal to drive an electrical load; and a controller insignal communication with the transmitting power converting circuit andthe receiving power converting circuit, the controller configured toactively adjust one or both of transmitting phase angles of thetransmitting elements and receiving phase angles of the receivingelements, wherein the controller actively adjusts one or both of thetransmitting phase angles of the transmitting elements and the receivingphase angles of the receiving elements so that the transmitting phaseangles match the receiving phase angles.
 2. The power converter systemof claim 1, wherein in each transmitting element among the plurality oftransmitting elements are separated from one another such that eachtransmitting winding included with a respective transmitting element isseparated from one another, wherein in each receiving element among theplurality of receiving elements are separated from one another such thatthe each receiving winding included with a respective transmittingelement is separated from one another, and wherein the plurality oftransmitting elements are separated from the receiving elements by anair gap.
 3. The power converter system of claim 2, wherein thetransmitting power converting circuit is a direct current-to-alternatingcurrent (DC-AC) converter having an input connected to a prime powersource to receive the input power signal, and an output connected to theplurality of transmitting elements.
 4. The power converter system ofclaim 3, wherein the DC-AC converter includes a plurality of switchesconnected in a bridge configuration to form a first bridge comprising abi-directional dual active bridge (DAB) circuit.
 5. The power convertersystem of claim 3, wherein the receiving power converting circuit is anAC-DC converter having an input connected to the plurality of receivingelements to receive the transferred power signal, and an outputconfigured to deliver the output power signal.
 6. The power convertersystem of claim 5, wherein the AC-DC converter includes a secondplurality of switches connected in a bridge configuration to form asecond bridge of the bi-directional dual active bridge (DAB) circuit. 7.The power converter system of claim 6, wherein the first bridge of thebi-directional dual active bridge (DAB) circuit includes a filtercircuit connected between a pair of switches among the first pluralityof switches and a transmitting element among the plurality oftransmitting elements.
 8. The power converter system of claim 7, whereinthe second bridge of the bi-directional dual active bridge (DAB) circuitincludes a capacitor connected between a pair of switches among thesecond plurality of switches and a receiving element among the pluralityof receiving elements.
 9. The power converter system of claim 6, whereinthe plurality of transmitting elements are connected in series with oneanother, and the plurality of receiving elements are connected inparallel with one another.
 10. The power converter system of claim 1,wherein a first transmitting winding of a first cell is formed on afirst insulating layer, and second transmitting winding is formed on asecond insulating layer different from the first insulating layer. 11.The power converter system of claim 10, wherein the first winding andthe second winding are separated from one another.
 12. The powerconverter system of claim 1, wherein the transmitting power convertingcircuit includes a first plurality of switches and the receiving powerconverting circuit includes a second plurality of switches, and whereinthe controller actively controls one or both of a first switchingfrequency of the first plurality of switches and a second switchingfrequency of the second plurality of switches such that the firstswitching frequency matches the second switching frequency so that thetransmitting phase angles of the transmitting elements match thereceiving phase angles of the receiving elements.